Some peculiar elements in the rotifer fauna of the atlantic sahara and of the atlas mountains

In addition to ubiquitous forms, the Adrar of Mauretania has a number of rare tropicopolitan species, which occur here in relative abundance. In the Moroccon Atlas mountains, West-African forms meet boreo-alpine forms. A population of Hexarthra from Atar, Mauretania, was intermediate between the fennica-group and the jenkinae-group.